1. Field of the Invention
The present invention relates to trailer hitches, including receiver, gooseneck, and fifth wheel type hitches for attachment to automobiles, trucks, tractor-trailers, and other vehicles. More particularly, the present invention relates to a trailer hitch with a slidably connected frame and carriage, wherein a multi-directional dampening system is operably connected between the frame and the carriage. The invention further relates to adapters for interfacing the trailer hitch to various trailer/vehicle combinations.
2. Discussion of Background
Trailers can be connected to tow vehicles by any of a variety of hitches, ranging from simple ball hitches and receiver hitches to heavy-duty gooseneck and fifth wheel hitches. The selection of hitch for any particular application depends on a number of factors, including the type of vehicle, the dimensions and weight of the trailer, and the anticipated load (including the weight, dimensions, and type of load). Hitches are available for virtually any motor vehicle on the market today: ball type hitches and receiver hitches are more commonly used with passenger vehicles and light trucks (automobiles, pick-up trucks, and the ever-popular sport-utility vehicles or SUVs) for light-duty hauling. Gooseneck and fifth wheel type hitches are used with heavy-duty pickup trucks and tractor-trailers used for hauling heavier loads.
While in motion, all vehicles and all trailers tend to bounce or sway to some degree; the extent of such bouncing or swaying motion depends on the vehicle""s speed and road conditions. When a trailer T is attached to a tow vehicle V by a standard lock-down or solid connection hitch H as shown schematically in FIGS. 1A and 1B, the trailer cannot rotate about its center of mass and therefore cannot move independently of the vehicle. As a result, any bouncing, swaying, and vibration of trailer T is transferred directly to vehicle V through hitch H, leading at best to an uncomfortable ride for the driver and passengers. Movement of trailer T relative to vehicle V in the vertical direction is represented by arrows A in FIG. 1A; relative movement in the horizontal direction is represented by arrow B in FIG. 1B. The safety of the driver and passengers is compromised whenever the relative movement of the trailer makes it more difficult to control the vehicle, for example, if the driver encounters high bumps, dips, railroad tracks, elevation changes, expansion joints, and situations that require emergency braking (which can cause jack-knifing) or other avoidance maneuvers. As trailer T bobs, bounces, and weaves, the back of vehicle V can sometimes be lifted off the road; the front end of the vehicle may also be lifted in turn and pushed from side to side, creating extremely dangerous conditions. Analogous concerns are found in other situations where a movable object is attached to a vehicle or a fixed support structure: boat docks, loading docks, airplane boarding bridges, and the like.
These problems are addressed by a variety of designs for trailer hitches and like apparatus. By way of example, Van Vleet (U.S. Pat. No. 5,823,560) discloses a trailer hitch apparatus with dampening mechanisms. The apparatus includes a hollow draw bar tube that can be coupled to a receiving tube mounted to a vehicle, and a ball hitch assembly carried by a transverse support bar attached to the outer end of the draw bar tube. The tube can move longitudinally with respect to the receiving tube; the ball hitch assembly is biased against vertical movement.
Gibbons (U.S. Pat. No. 5,413,366) shows a vertically adjustable hitch with a stationary portion that can be inserted into a trailer hitch tongue. The hitch includes a slider that is vertically movable with respect to a guide plate; the vertical position of the slider can be fixed via a pair of holes that can be aligned with respective detents of the guide plate. Jacks (U.S. Pat. No. 4,215,876) discloses a trailer hitch having a planar sliding plate mounted between a pair of spaced-apart, parallel vertical guides. A tongue extends outwardly from the slide; a conventional ball hitch is attached at the end of the tongue, and an adjustable-force leaf spring minimizes the transmission of shocks and vibrations between the tow vehicle and the load by providing variable resistance to vertical travel. Kendall (U.S. Pat. No. 3,400,949) describes a trailer hitch with a vertically-adjustable ball. The ball is attached to a mounting plate that is movable within a channel to any of a plurality of positions. Whatoffs (U.S. Pat. No. 3,269,751) adjustable hitch includes a pair of spaced-apart coil spring assemblies, a pair of tubular members that are telescoped in tubes for horizontal movement towards and away from the truck body, and a ball-type hitch attached to a slide plate that is movable vertically in a channel. Logan, et al. (U.S. Pat. No. 5,836,603 and 6,116,631) describe a trailer hitch assembly with variable pressure air springs (also termed xe2x80x9cair bagsxe2x80x9d or xe2x80x9cpneumatic shock absorbersxe2x80x9d) connecting the hitch and the support.
Fifth-wheel hitches are generally used for heavy-duty applications. Vitale, et al. (U.S. Pat. No. 5,639,106) describe a tractor-trailer fifth wheel air suspension assembly with a mounting frame connected to a tractor body frame and a movable frame for supporting the fifth wheel. The movable frame is supported on the mounting frame by a two-point or four-point air suspension system which stabilizes the trailer load when hauling. The movable frame has slides which are received in channels on the mounting frame. Noah, et al. (U.S. Pat. No. 5,226,675) discloses a fifth wheel suspension apparatus designed to reduce the magnitude of changes in vertical force transmitted to a tractor from a trailer. The apparatus includes a sensor, an actuator and a controller. The sensor transmits a signal indicating the vertical force transmitted from the trailer through the fifth wheel hitch to the controller, which then varies the amount of vertical force applied to the fifth wheel hitch by the actuator. The apparatus includes an air spring for adjusting the displacement of the hitch from the tractor. Bauer (U.S. Pat. No. 5,209,316) provides a truck cab suspension unit with two U-shaped yokes, an air spring, and shock absorbers. Funk (U.S. Pat. No. 3,227,470) provides a tractor-trailer load transferring device that includes an air bag assembly positioned between two pairs of guide tubes, each tube having a slidable guide rod therein. Masser (U.S. Pat. No. 3,137,515) discloses a fifth wheel structure that includes a pair of air bags that support one of the fifth wheel, the structure functions as a conventional fifth wheel if the air bags should fail. Gouirand (U.S. Pat. No. 2,968,496) shows a pneumatic chamber rigidly mounted at the rear of a truck frame. The chamber, which has a circular cross-section, has a lower diaphragm connected to the rear axle of the trailer; an upper diaphragm supports the lower plate of a fifth wheel assembly. Reid, et al. (U.S. Pat. No. 2,733,931) provide a fifth wheel suspension that includes a pair of air springs; the degree of cushioning provided by the air springs is automatically adjusted to compensate for changes in the load.
Special-purpose hitches include those designed for hauling mobile homes. For example, Kingsley, et al. (U.S. Pat. No 4,564,209) disclose a trailer hitch assembly having a fixed frame attachable to the rear of a truck, a transverse carriage mounted to the frame, a piston, and ram assemblies for moving the carriage vertically and laterally with respect to the frame. The assembly includes two sets of roller assemblies, each with three sets of rollers and associated channels. Brockmiller""s (U.S. Pat. No. 4,153,270) apparatus includes a tiltable sliding hitch-ball holder and a guide rack where pin-mounted rollers guide the vertical movement of a carriage on a pair of vertical poles. The sliding hitch-ball holder is raised on the poles by dual cylinders, and telescoping poles connect the upper end of the apparatus to a crossbar at the rear of the truck. Taylor (U.S. Pat. No. 4,148,498) describes a trailer hitch with a hydraulically elongatable tongue and an adjustable connector ball assembly; hydraulic cylinders and springs adjust the tongue and the height of the connector ball. Grace (U.S. Pat. No. 4,057,265) provides a towing apparatus having three control levers that allow the operator to adjust the position of a hitching ball forward and rearward, laterally, and vertically with respect to the tow vehicle. The apparatus includes several hydraulic cylinders and several sets of rollers that move in corresponding horizontal or vertical channels. Dutton (U.S. Pat. No. 3,865,406) shows a horizontally movable gear plate and standard hitch ball that is movable vertically in a slideway via a rack-and-pinion arrangement. The slideway has a pair of opposing vertical guide rails. Jones (U.S. Pat. No. 3,708,183) discloses a trailer hitch having a fixed frame attached to the rear of a tow vehicle, a drawbar resiliently mounted to the frame, and a standard ball-type connector attached to the drawbar. The fixed frame has two spaced-apart vertical channels that hold shock-absorbing compression springs. The drawbar rides on the springs; the ball connector is attached to a slide plate that is movable vertically in a channel formed by a pair of guide slots.
Other types of mechanisms for use with boarding bridges, docks, and other devices are available to consumers. Hansen, et al. (U.S. Pat. No. 5,704,086) describe a passenger boarding bridge for use with airplanes. The bridge has two slidable sections that move on rollers, and that can be raised and lowered by vertically-adjustable jacks. It includes stabilizing rollers or slide blocks. Godbersen (U.S. Pat. No. 5,427,471) shows a dock mounted boat hoist with a vertical main post mounted on a dock and a platform unit for supporting a small boat. The platform is slidably connected to the main post and a frame; a cable and winch are used for raising and lowering the platform. Wirges, et al. (U.S. Pat. No. 4,632,371) provide a gas spring for jumping stilts. Their device includes a plunger and a gas exchange chamber connected to the working chamber by a passage. The device allows the user to adapt the spring force to the his weight and level of skill. Montenare""s (U.S. Pat. No. 3,203,723) pneumatically-cushioned bumper has a plurality of telescoping sections whose movement is facilitated by rollers. Dreisbach (U.S. Pat. No. 2,150,269) shows a floating drawbar guide for tractors. His device includes a pair of springs (with pistons) within a casing that is slidable in a guide tube. Each of the springs also includes a piston. Hipp, et al. (U.S. Pat. No. 4,373,847) disclose a releasable locking device for securing a parked vehicle to an upright structure. Their device includes a fixed frame with a pair of spaced-apart, parallel guide tracks, and a ratchet mechanism and spaced-apart rollers for adjusting the height. Rosengren (U.S. Pat. No. 4,137,587) shows a dockboard with a pivotable ramp which is movable between a vertical, storing position and a horizontal, working position. The chassis includes a pair of rollers on each side; these help prevent locking of the chassis by skewing. Beckwith, et al. (U.S. Pat. No. 3,426,377) provide a dockboard with a carriage that is movable via rollers that move in a pair of spaced-apart vertical channels. The dockboard includes separate lip and platform sections which are independently rotatable about a common axis, and which can be locked together to form a ramp.
Many presently-available trailer hitches used for connecting a trailer to a tow vehicle are complex and expensive to manufacture, high-maintenance, or do not allow for optimum vertical and lateral movement of the trailer with respect to the vehicle. Conventional lock-down hitches in particular transfer any bouncing, swaying, and vibration of the trailer to the vehicle (and vice versa), resulting in an uncomfortable ride and potentially dangerous driving conditions.
These concerns are addressed in co-pending U.S. application Ser. No. 10/025,066, filed Dec. 19, 2000, which discloses a trailer hitch for attachment to a tow vehicle for towing a trailer. The trailer hitch includes a first support member including at least one pair of spaced-apart, substantially parallel tubes, a second support member including at least one slide block assembly configured for slidable movement in the tubes, and a variable pressure air spring operably connected between the support members, one of which is attached to the tow vehicle and the other to the trailer. In use, the slide block assembly and the air spring provide a measure of multi-directional dampening to reduce transmission of relative motion between said tow vehicle and said trailer.
Despite the variety of products of this nature that are available to consumers, there is a continuing need for a simple, rugged, durable and versatile trailer hitch that can be adapted for use with passenger automobiles and light pick-up trucks, heavy-duty pickups, trucks, and tractor-trailers.
According to its major aspects and broadly stated, the present invention is an adjustable trailer hitch with two support members, one of which is attached to a vehicle and the other to a trailer. The first support member, or frame, includes a generally vertical track; the second support member, or carriage, includes a slide block assembly configured for slidable movement in the track. A multi-directional dampening system is connected between the first and second support members, and mechanically isolates the trailer and the vehicle from each other. The invention also includes a variety of adapters for interfacing the trailer hitch to various vehicle/trailer combinations.
In one preferred embodiment of the invention, the frame is connected to the tow vehicle and the carriage to the trailer, with the slide block assembly engaging the track for slidable movement therein. In another preferred embodiment, the carriage is connected to the tow vehicle and the frame is connected to the trailer. While driving, the trailer hitch mechanically isolates the vehicle and the trailer from each other, providing multi-directional dampening of movement of the trailer with respect to the vehicle (and vice versa). Instead of acting as a single unit, the vehicle and the trailer act largely independently of each other: the bouncing, jerking, and swaying motions transferred from one to the other by many conventional hitches are reduced or eliminated, resulting in better control (for the driver) and a safer and more comfortable ride (for the driver, passengers, and load).
The multidirectional dampening system of the trailer hitch is an important feature of the present invention. The components of the system depend on the type of hitch (i.e., receiver, gooseneck, etc.), the vehicle, and the types and weights of loads to be carried by the trailer. The system may include at least one variable-pressure or adjustable-pressure air spring operably connected between the first and second support members, and, optionally, shock absorbers for helping absorb mechanical shocks. On receiver-type hitches, the system may also include at least one spherical rod-end assembly connected between the first and second support members for helping stabilize relative movement between them.
For purposes of this specification, the term xe2x80x9cspringxe2x80x9d refers to an elastic device that regains its original shape and/or position after being compressed or extended. The terms xe2x80x9cair springxe2x80x9d and xe2x80x9cpneumatic springxe2x80x9d refer to a type of spring in which the energy storage element is air (or other gas) confined in a container that includes an elastomeric bellows or diaphragm. The term xe2x80x9cshock absorberxe2x80x9d refers to a device for absorbing mechanical shocks, that is, for minimizing the acceleration of the mass of a mechanism or portion thereof with respect to its support. (Automobile shock absorbers include hydraulically dampened couplings for absorbing impulsive forces generated by the contact of automotive wheels with irregular road surfaces.) In colloquial usage, air springs are sometimes referred to as xe2x80x9cair shock absorbersxe2x80x9d or xe2x80x9cpneumatic shock absorbersxe2x80x9d; however, those skilled in the art avoid this usage in order to preserve the distinction between air springs and shock absorbers.
The combined action of the air spring, the spherical rod-end assembly, and the slide block assembly substantially reduces transmission through the trailer hitch of any relative movement of the trailer and the vehicle, thereby improving driver control as well as providing increased comfort and safety. When driving over bumps, potholes, railroad tracks, and the like, up-and-down, side-to-side movement of the trailer and the vehicle is substantially absorbed by the trailer hitch while continuing to move and turn as a single unit under the driver""s control, relative movement of the trailer with respect to the vehicle is no longer transferred to the vehicle (and vice versa). This dampening action reduces transfer of trailer bouncing and swaying motions by as much as 80% over conventional lock-down hitches.
The spherical rod-end assembly is another important feature of the present invention. The spherical rod-end assembly includes at least one rod end operably connected between the first and second support members (i.e., the frame and the carriage) by generally spherical, swivel-type connectors. The connectors permit the rod end to rotate with respect to the support members. In all hitches that include the spherical rod-end assembly, the action of the assembly tends to stabilize the trailer hitch and further its multi-directional dampening action.
The combination formed by the slide block assembly and the track constitutes another feature of the present invention. The track is configured to receive the slide block assembly, which is configured and positioned to mate with the track when the trailer hitch is assembled. The track is preferably made of a sturdy, durable material such as stainless steel, aluminum or the like, and forms a channel that slidingly contains the slide block assembly, and preferably substantially enclose the slide block assembly when the trailer hitch is assembled for use. If desired, wear strips may be installed in the track to help extend the working life of the trailer hitch. The optimum configuration of the slide block assembly depends on the particular application. For example, the slide block assembly may include a single low-friction slide block attached to one of the first and second support members, a pair of low-friction slide blocks, or a plurality of pairs of slide blocks with a corresponding number of pairs of tracks. The slide block (or blocks) may be made of any suitable low friction material (such as ACETAL, NYLATRON, NYLON, TEFLON, or other suitable material) attached to suitable mounting blocks; alternatively, the slide block may be made  of a metal core with a low-friction coating.
Still another feature of the present invention is the air spring, which connects the frame and the carriage to help dampen transmission of movement from the trailer to the vehicle (or vice versa) and also furthers adjustment of the trailer hitch for different loads. In a preferred embodiment of the invention, the air spring is a adjustable-pressure, single or double bellows type air (i.e., pneumatic) spring of the type sometimes referred to as an xe2x80x9cair bag,xe2x80x9d xe2x80x9cair spring,xe2x80x9d or the like (for purposes of this specification, the terms xe2x80x9cair spring,xe2x80x9d xe2x80x9cair bag,xe2x80x9d and xe2x80x9cpneumatic springxe2x80x9d are used interchangeably). The air spring can be a manually-inflatable or automatically-inflatable type; these types of air springs can readily be inflated with a portable compressor, with an air hose (at service stations or other facilities), or with an on-board compressor and control system accessible to the driver of the tow vehicle.
Changing the pressure in the air spring helps adjust the trailer hitch for different types and weights of load. (While hydraulic or mechanical springs may also be useful, air springs are preferred because of their adjustable pressure.) If the air spring accidentally loses pressure, the trailer hitch functions as a conventional solid hitch (also known in the art as a lock-down hitch) until the driver can effect any needed repairs.
Yet another feature of the present invention is the adapters which are used to interface the trailer hitch between different types of vehicles and trailers. The adapters, which include weight distribution brackets, sway-bars, quick-change mounts, retainers, safety chains, spreader bar assemblies, spacers, and mounting plates having a plurality of user-selectable positions for attachment of the trailer hitch, allow the user to interface the invention with most presently-available vehicles and trailers. The adapters may also help adjust the invention for different loads.
Another feature of the present invention is its versatility. The invention can be configured as a receiver type hitch, a gooseneck type hitch, or a fifth wheel type hitch, in virtually any needed pin weight and towing capacity. The particular selection of components and materials for the trailer hitch depends on the specifications of the vehicle and the trailer, the anticipated loads to be carried by the trailer, and other factors evident to those of ordinary skill in the art.